73493-56-8Relevant articles and documents
BIOSYNTHESIS OF THE POLYETHER ANTIBIOTIC MONENSIN-A. RESULTS FROM THE INCORPORATIONS OF LABELLED ACETATE AND PROPIONATE AS A PROBE OF THE CARBON CHAIN ASSEMBLY PROCESSES
Sood, Gulshan R.,Ashworth, Doreen M.,Ajaz, Abid A.,Robinson, John A.
, p. 3183 - 3194 (2007/10/02)
The incorporation of sodium - and (S)--propionate into the polyether antibiotic monensin-A in cultures of Streptomyces cinnamonensis occurs with retention of label only at C-4 and C-6, whereas during the incorporation of sodium (R)-propionate the deuterium label is lost to the medium.These results are consistent with the formation of (S)-methylmalonyl-CoA from the labelled propionate by carboxylation of propionyl-CoA with loss of the 2-pro-R hydrogen.The (S)-methylmalonyl-CoA is subsequently incorporated into the antibiotic by a decarboxylative condensation occuring with overall inversion.The incorporations of sodium -and -acetates into monensin-A provide evidence for a pathway of metabolism leading to methylmalonyl-CoA that does not proceed via succinyl-CoA.Instead, acetyl-CoA may be processed via butyryl-CoA and isobutyryl-CoA, to afford (S)-methylmalonyl-CoA.
Characterisation of the citrate synthase reaction with propionyl-CoA.
Brand?nge,Josephson,M?hlén,M?rch
, p. 695 - 700 (2007/10/02)
Experiments with propionyl-CoA stereoselectively deuteriated in the propionyl moiety demonstrate that the formation of (2S,3S)-methylcitric acid (1) catalysed by citrate (si)-synthase occurs with inversion of configuration in the propionyl moiety; the absolute configurations of the methylcitric acids 1 and 2 indicate a si attack on oxaloacetate. Deuterium in the pro-S position is exchanged for protium 60 times faster than deuterium in the pro-R position. Experiments with (R,S)-(2-2H1)propionyl-CoA allowed the determination of isotope effects. For the enzymatic formation of 1, a primary deuterium isotope effect kH/kD = 1.8 and a secondary alpha-deuterium isotope effect kH/kD = 0.99 were calculated; both are effects on Vmax/KM.
